Production of alkyl derivatives of thiophene



Oct. 5, 1948.

H. E. RASMUSSEN ET AL 4 PRODUCTION OF ALKYL DERIVATIVES OF THIOPHENEFiled Sept. 29, 1944 INVENToRs HERBERT :'.RAs/w/ssE/v Row/ m10 c.HANS/ORD Patented Oct. f, 1948 PRODUCTION G F ALKYL DERIVATIVES `0FTHIOPHENE Herbert E. Rasmussen and Rowland C. Hansford, Woodbury, N. J.,assignors to Socony-Vacuum Oil Company, Incorporated, a corporation ofNew York Application september 29, 1944, serial No. 556,438

Claims.

This invention relates to the manufacture of alkyl derivatives ofthiophene, and is more particla'rl'y concerned with a process forproducing falk'yl derivatives of thiophene from aliphatic hydr'ocarbonscontaining ve and six carbon atoms.

Methyl thiophene and dimethyl thiophene as Well as thiophene are Wellknown compounds and 'coed-r, Aordi-narily, in the toluene, xylene andben- 'ze'n'e fractions, respectively, of -coal tar distillate's. Theamounts of methyl th-iophene and of dimethyl thliophene usually presentin the crude toluene and v`izylene fractions respectively, are of the4order of about 0.5%. The close proximity 'o'fthe' boiling point-s ofthiop'hene and benzene, 'of methylthio'phene and toluene, and ofdimethyl thiop'hene v'and xylene', renders the complete separation andrecovery of these compounds from the corresponding fractions, byfractional distillation, a somewhat 'di'iicult operation. Consequently'commercial benzene normally' contains f traces fof thi'ophene, fandcommercial toluene land xylen'e lcontain 'traces of lmethyl thiopheneand of dimethyl thiophene, respectively. However, since thiophene andthe alkyl thiophenes are amenable to vsulfonation much more readily thanbenzene, toluene and xylene, thiophene and the alkyl thiophenes-'can beremoved from benzene, tolueneand xylen'e in the form of theirs'u'lfonates, by repeated treatments with concentrated sulfuric acid.rThis, of course, is `an expensive operation.

Thiophfene has been synthesized ina number of Ways. 'In' accordance withthe syntheses of the priorY ar-t, acetylenev 'has constituted apreferred source'of-tlfiio1crhfene`- Thus, it has been proposed toproduce thiophene by reacting acetylene with pyrites, with hydrogensulfide in the'presence lof Icatalytic material, 'with sulfur in thepresence or absence of catalytic material, 'and with 'carbon disulfide.`@ther` Asyntheses proposed have Vinvolved-'the reaction of other'hydrocarbons with sulfur Vor hydrogen sulde in the presence of variouscatalytic-materials. Thiophene has been produced' also from butylm'ercaptan by' dehydrogenation and cyclizati'on, by' cycliz'ati'on ofother organ-ic 'compounds by interchange of -heteroatoms in heterocycliccompounds, etc. It must be noted, however, that the' yields of thiophenein alt of these syntheses generally, have been `poor, in some cases onlytraces of thi'ophene orderivatives thereof being produced.

*Ehe inherent Ichem-ical character 'of -thiophene and-'of alkylderivatives of thiophene, indicates a potentially Wide use 'of thesecompounds in industrial-applications; however, the costly nature f 'Withsulfur.

2 of the methods of separating and recovering thiophehe from crudebenzene and of synthesizeA ing thiophene and alkyl derivatives ofthiophene, have 4somewhat limited the use of theselcofnpoundscommercially, the only present outlets of any consequence, being thedrug `and dye elds".

Various attempts have been made to provide cheap and commerciallyfeasible processesfor producing thiophene; but and as notedhereinbefore, processes embodying the methods known to the prior art,have suffered from two disadvantages, the rst being the availability andcon-4 sequently, the cost of the lcharging stocks, 'and the second beingthe magnitude of the yields of thiophene achieved. Thus and as is wellknown to those familiar with 'the art, when the charge stock of a givenprocess has been readily available and its cost, therefore, has beenrelatively low, the' yields of thiophene have been small; on the otherhand, when `the yields have been high, the cost of the charge stock hasbeen high. c

`In the search for readily available and cheap charge stocks tosynthesize organic compounds generally, butane and heptane have beenreacted These reactions were carried out to determine whatcompoundswould be formed and not for the express purpose of synthesizingthiophene or alkyl thiophenes. However, not more than a mere tr'ace ofthiophene and no alkyl thiophenes werel obtained. [Baker and Reid, Jl,Am. Chem. Soc., vol. 51, p. 1566 (1929).]

A copending application, Serial Number 556,150 lle'd September '28,1944, is directed to a process for manufacturing thiophene, whichcomprises separately preheating sulfur and one or more normal aliphatichydrocarbons containing four carbon atoms, to temperatures such that bycombining :the sulfur and hydrocarbon material, Will give av mix-ture'having a temperature varying between about 850 F. and about 1400o mixingthe preheated ysulfur and hydrocarbon material, maintaining the'temperature yof the mixture at temperatures in excess of about 850 F.for a period of time of less than about one second, and reducing thetemperaturev of the mixture to less than about 850 F.

We have discovered that alkyl derivatives of thiophene `may be producedin substantial amounts, by 'reacting aliphatic hydrocarbons v:containingve or six carbon atoms, with sulfur at elevated temperatures and underclosely con-v trolled reaction conditions.

We -have' now found that methyl thiophene may be obtained A-by reactingaliphatic hydrocarbons containing ve car-bon atoms, with sulfur atEele-V 3 vated temperatures and under closely controlled reactionconditions, and that dimethyl thiophene and ethyl thiophene may beobtained by reacting aliphatic hydrocarbons containing six carbon atoms,with sulfur at elevated temperatures and under closely controlledreaction conditions.

Accordingly, it is an object of the present invention to provide a cheapprocess for producing alkyl derivatives of thiophene. Another object isto provide a cheap and readily available source of alkyl derivatives ofthiophene. A further object is to provide a process for producing alkylderivatives of thiophene that is commercially feasible. A more specicobject is to provide a process for obtaining high yields of methylthiophene, ethyl thiophene and dimethyl thiophene from aliphatichydrocarbons containing five and six carbon atoms. A very importantobject is to afford a process capable of carrying out the above objectsby reacting aliphatic hydrocarbons containing ve and six carbon atoms,with sulfur at elevated temperatures and under closely controlledreaction conditions.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art from the following descriptiontaken in conjunction with the drawing, in which the single figurerepresents a diagrammatic illustration of a plant for practicing theprocess of our inven tion.

Broadly stated, our invention provides a process for manufacturing alkylderivatives of thiophene, which comprises separately preheating sulfurand one or more aliphatic hydrocarbons containing live or six carbonatoms, to temperatures such that by combining the sulfur and hydrocarbonmaterial, will give a mixture having a temperature in excess of about850 F., mixing the sulfur and hydrocarbon material, reacting thepreheated sulfur and the preheated hydrocarbon material at temperaturesin excess of about 850 F. for a period of time of less than about onesecond, and reducing the temperature of the mixture to less than about850 F.

A feature of the process of the present invention is that with theexception of hydrogen sulfide, alkyl thiophenes are the principalsulfurcontaining compounds obtained. A tar, probably a mixture ofcomplex hydrocarbon polysuliides, containing about 75% sulfur is alsoproduced. The sulfur in this tar can be recovered and recycled.Mercaptans and carbon disul-de are also formed, but these only in smallamounts. The hydrogen sulfide obtained may be regenerated almostquantitatively back to sulfur for use in the process, by a veryinexpensive treatment, such as incomplete combustion into water andsulfur.

Another feature of the process of the present invention is that thematerials in the charge, i. e., aliphatic hydrocarbons containing ve andsix carbon atoms and sulfur, are cheap and plentiful. Generallyspeaking, any aliphatic hydrocarbon having five or six carbon atoms andcontaining at least four carbon atoms in a chain, is suitable for theprocess of our invention. 'I'he aliphatic hydrocarbons may be derivedfrom any suitable source, as is well known in the art, and may consist,for example, in the production of methyl thiophene, either of pentane orisopentane or pentenes or isopentenes or even pentadienes, or mixturesof them, On the other hand, in the manufacture of dimethyl thiopheneand/or of ethyl thiophene, the aliphatic hydrocarbon charge may consisteither of hexane or isohexane or hexenes or isohexenes or evenhexadienes, or mix- 4 tures of them. It should be observed, however',that for economical operation of our process, pentadienes per se, andhexadienes per se cannot be processed successfully because of thetendency of these Idioleiinic hydrocarbons to polymerize under theconditions of the process.

An important feature of our invention is that in our process thereaction is highly selective. High yields of alkyl derivatives ofthiophene are obtained, and they may be recovered from the reactionproduct in a highly pure state using conventional and readily availablefractionating equipment.

A very important feature of the present invention is that it provides acheap and eiicient method of producing alkyl derivatives of thiophene.In our process, no catalysts are employed, thereby avoiding thedisadvantages attendant on their use, such as regeneration andreplacement problems, as well as the use of special reaction chambers.The process is substantially a one-step process, although as willsubsequently be seen, appreciable amounts of pentenes or hexenes and ofpentadienes or hexadienes may be found in the eiiluent from the reactionzone. These may be recycled to the reaction zone for further conversioninto alkyl derivatives of thiophene, thereby increasing theoverall-yield of the desired products. The equipment required isessentially only a pair of corrosion-resistant alloy preheaters, acorrosion-resistant alloy reactor coil and a corrosion-resistantcondensing system. The separation of hydrogen sulde presents fewdiiculties, since most of it can be removed by suitable stabilizingequipment and the last traces removed by caustic scrubbing or otherconventional hydrogen sulfide removal processes.

While relatively large quantities of sulfur are employed, it isnevertheless one of the cheapest and most non-critical chemicalreagents. We have found, in the operation of our process, that therelative proportions of sulfur and hydrocarbon material may be variedover wide limits. However, too much sulfur results in poor efficiency insulfur utilization per pass and favors the complete oxidation ofhydrocarbon material to carbon disuliide. On the other hand. too low aproportion of sulfur lowers the conversion per pass and the ultimateyield by increasing the overall thermal degradation of hydrocarbonmaterial. Best results are obtained using a weight ratio of sulfur tohydrocarbon material varying between about 0,5 and about 4.0, althoughwhen pentenes or pentadienes, or hexenes or hexadienes constitute thebulk of the hydrocarbon material in the charge, the lower limit of theweight ratio may be lower than 0.5.

The selectivity of the reaction involved in the process of the presentinvention depends primarily upon two variables, namely, reactiontemperature at'which the aliphatic hydrocarbons containing ve or sixcarbon atoms are contacted with sulfur, and reaction time or the timeduring which contact between the reactants is maintained at the reactiontemperature.

T-he limits of operating temperature are fixed by the kinetics of thedesired reaction and the kinetics of possible side reactions. We havefound that the reaction temperature may vary between about 850 F. andabout 1300 F., and preferably, between about 1000 F. and about 1200 F.Below the lower limit of the temperature range, the reaction is so slowas to require a large through-put of sulfur and a higher ratio ofhydrocarbon recycle .for a fixed amount of end product, thereforedetract-ing from the economics i'f the operation; Further, the secondaryreaction of 'tar "formation con'su'rri'es y'a larger proportion of thecharge. Above the upper limit of the temperature v range, -the secondaryreaction of de- 'gradation Aof hydrocarbon material in the charge takesprecedence, thereby decreasing 'the l*yield of :desired product. VItmust 'be noted, also, that 'at these high temperatures, corrosion"problems are-'at aimaximum, corrosion increasing percep tibly 'withincreasing temperature.

expecteiwehave found that the optimum reaction time depends upon thetemperature 'em'- ployed. Generally speaking, othervariable'sfr'emaining constant, the lower the temperature, Vthe longervthe reaction time. The reaction or contactftinie"and the reactiontemperature'are somewhat'xed, `one in relation to the other, lby thedegree "of 'degradation of the 'hydrocarbon materiali'n Ethe charge, and`by the "extent to which undesirable products are formed,` which may betolerated. Thus, too long a contact time at high temperatures, results'in severe cracking of ythe hydrocarbon 'material in the charge. The'reaction which is highly endothermic, proceeds With ertreme speed, theonly limitation apparently bein'gftherapidity with which 4heat can besupplied to the reaction mixture. The lower limit of the range'of-reaction time is fixed, therefore, by the engineering ,problem of heattransfer and by mechanical limitationssuch `as allowable pressure dropacross the reactor. r'oo long a reaction time at temperatures in theneighborhood of the lovve'r limiter 'the temperature range, results inlower overall vyields of alkyl thiophenes due to increased 'formation ofheavy tar. On the other hand, 'too short a rreaction time attemperatures in the neighborhood vof the lower limit of the temperaturerange, results in incompletereaction. 'Inview of the foregoing, thecriteria to be used :in'determining optimum operating temperatures andreaction times are to choose the degree of conversion desiredcommensurate With 'pratin'gcost'such as heat input and equipmentcstajbearin'g Ain mind that the shorter the reaction 1time randconcoi'd'antly, the higher the temperature, the vlarger the amount ofend product whichfcafn be realized from a unit of given size perd-ay. Wehave found that the optimum re- "action time for the temperature rangeused in our process,"'about 850 F. to about 1300 F., varies betweenVabout 1;() second and about 0.01 second.

' The necessity for closely controlled reaction time fat theselectedreaction temperature renders the separate preheating ofthereactants essential. Heating the hydrocarbon material and the sulfurtogether has two undesirable effects. In the firstfpl-ac'e, at lowertemperatures, the reaction producing tar formation is the favored re-Ilaction; and in rthe vsecond place, these heavy productsaresubsequently cracked in the reactor at the'selecte'dreactiontemperature, causing undue coking. Tests have shown that Whenthe reactants 'are heated together up to temperatures withihftheaforementioned reaction temperature `rang`e,'tar formation alwaysresults, and'in such Yquantities, that the reaction zone is eventuallyplugged tup' lwith a heavy, carbonaceous deposit.

Accordingly, itis essential in our process to separtely preheat each ofthe reactants, i. e., the hydrocarbon or the mixture of hydrocarbonsconstituting *the hydrocarbon reactant and sulfur, to such temperaturesthat When they'are brought tbg'ether,runderproper conditions of flow, aternpratu're lfall'in'g'within the reaction temperature range 'ii-s-acl'iievd, before ieffecting" contact between them. In practice, thisLis effected 'ordrnarily, by separately preheating eachofthe ireactantsto temperatures within the reaction tem'- perature range.

As stated herein'before, we have ifoiind, io're'oo'- nomical operationofthe process, that pentadiene orhexadiene alone, cannot be lused as:the hydrocarbon "reactants because of 'their t'rideldy to fpolymeriz'ein the 'preheatert'vith consequent cracking .and severe coking in thereactor.y Hrvever, 'when pen-tadiene or hexadiene lare used inconjunction with pentanes and/oi` pentenes, or with hexanes fand/orhexene's, respectively, 'or with suitable 'diluents which are 'inertwith irespect to sulfur "'-and to other reaction products "'ff thelprocess, for example nitrogefn, carbon disulfide, carbon4dioxic'iefetc., they can be processed satisfactorilyI to give highyields of 'alkyl derivatives of thiophene. For 'e'ffectiveoperationofour process, We have 'found that pentadien'es or hc'X'a'- die'nes shouldnot rconstitute "more than "about 30% b'y volume of ythe hydrocarbonmaterial Iin the charge. v

lIn our "process, thereaction is effectedfprefer'- ably, at atmospheric`press-ure or under sufficient pressure to cause the `iiovv of thereactants through the reactor and auxiliary system, the desired reactionconditions. We `have found that best results are obtained whenturbulentiflow is maintained through fthe reactor, suitably, f

conventional `coil-type pipe reactor. With type of reactor, "the desiredturbulent ow may' be `achieved with apressure-drop'of 'about 2 to20lpounds` :across th'ecoil; depending upon the's'ize ofthe pipe yand thelength of 'the coil. "Turbullent ow promotesheattransfer and assuresgood mixing ofthe reacting 'vaporsof sulfur and hydrocarbon material. y

After the lpreheated hydrocarbon r'eactant and sulfur are 'mixed andallowed to react for vthe speciiied reaction time, the temperatureoffthie reaction Amixture is immediately lowercdto 'bie'- low about'" inorder to 'avoid'over-reaction in the system Yafter leaving vthe reactor.y"I'l'iis fmay vbeyaccompiisiied suitably vtyspraying the efiiuent ofthe reactor With aliquid.

R'ecycling'of the unreacted portion 'of "hydro"- carbon materialintheeiiluent stream, has been 'found lto be a vdesirable vscheme A'forincreasing the ultimateyield lofdesired product.

This has Vthe samee'ffect as lengthening-the reactiontime without theattendant and undesirable degradation of hydrocarbon'material, referredto hereinlbefore. 1When the paraflinichydrocarbons "are Ythehydrocarbonreactants, it isl suspected that the reaction proceeds stepwise 'withthe formation vof the corresponding oleiinic hydrocarbons, diolenichydrocarbons and iinally, alkyl Ithio- A"phenes, each step causing theformationjsimul'- taneous'ly,"of hydrogen sulfide, molecular Weight formolecular Weight. These reactions occur concurrently and unreactedlpentane or hexane "as well `aspe'ntenes or hexenes'and pentadi'enes orhexadienes arelfound in the eiluent. Only traces of acetyl'eriichydrocarbons 'have 'been Afound. The hydrocarbons in the eiiluentserveas recycle stream in the recycling operation. In this connection, itmust be observed that when pentenes or hexenes are the sole constituentsof the hydrocarbon reactant, 'recycling'of lthe 'hydrocarbons in the'eiliuent is not commercially vfeasible 'ih'view lof' the highconcentration of peri- 'tadiene's for hexadienes, respectively, 'in 'theI re;-

eycie stock. "Hwever, and as Stated hereinte1 fer to the reactionmixture.

7 fore,'pentanes or hexanes, or other suitable diluents may be added tothe recycle stocks and the latter processed to give high yields of alkylderivatives of thiophene.

Accordingly, .a most important feature of our process, is that it isilexible, itbeing possible to produce pentenes or hexenes as well aspentadenes or hexadienes from pentane or hexane, or pentadienes orhexadienes from pentenes or hexenes, respectively, in addition to alkylthiophenes. -A plant for practicing the process of our invention isillustrate-d diagrammatically in the drawing. It is understood, ofcourse, that certain modications of this operating Scheme, as well aschanges in the type of equipment employed,lmay be made as long as theessential requirements of the process `are maintained, as will beobvious to those skilled in the art, once .theconditions .ofV theprocess, with which this invention is concerned, are clearly understood.

y Referring now more particularly to the drawing, pentane is pumped froma storage sphere 4 by a pump 5, to a preheater coil E. Molten sulfur ispumped from a storage tank I by a pump 2, to a preheater coil E3. Thepreheated vapors of pentane and sulfur are mixed at a point I prior tointroduction into the reactor, and are then sent through a reactor coil8. The preheaters 3 and 6 vand the reactor 8 may each be in separatefurnaces if desired, or, if in the same furnaces, as shown, may be ofdifferent lengths to produce ,the desired preheating temperatures andreaction temperatures. As stated hereinbefore, one very essential factorof the process is that short reaction times must be used.` This requiresrapid mixing of the reactants and rapid heat trans- The reactionproducts enter a spray chamber 9 where they are quenched to atemperature of about 300 F., by spraying suitably with crude methylthiophene or some other liquid product of the process. The quenchedreaction products subsequently are passed into a tar-separator I0,wherein tar separates out and is sent to a sulfur-recovery plant I9.'I'he reaction products free of the bulk of the tar, go to a lter Il, toseparate the tar mist. A Cottrell precipitator may be used as the mistcollector if desired. The ltered products are then passed into acondensate stripper column I-2 where most of the products that arenormallyliquid are stripped out. This column may be operated as anabsorption stripper by using methyl thiophene bottoms as the absorberliquid. The liquid bottoms from the condensate stripper column I2, go toa carbon disulfide tower I 'I and the overhead to a compressor I3 andthence to a column Idwhere ca-hydrocarbongases, gases lighter thanCa-hydrocarbons and hydrogen suliide are removed as overhead and sent tothe sulfur-recovery plant I9. The bottoms from the column I4, consistingof Ci-hydrocarbons and materials having boiling points higher than C4-hydrocarbons, are passed into a column I 5 where Ci-hydrocar-bons areobtained as overhead. 'I'he bottoms from column I5, consisting ofCs-hydrocarbons and materials having boiling points higher thanCs-hydrocarbons, are passed into a column 20 where Cs-hydrocarbons areobtained as overhead, combined with the overhead from the debutanizercolumn I5, and recirculated through a meter I6 to the preheater 6, andthus returned to the process as recycle stock. The bottoms from thecolumn 20 are combined with the bottoms from the condensate strippercolumn I2, and sent to the carbon disulfide tower I1. Carbon disulde istaken off as overhead from the tower I'I and sent to storage, while thebottoms from the tower II are passed into a thiophene tower I8 wherethiophene produced as a result of some cracking of G51-hydrocarbons toCir-hydrocarbons, is taken as overhead and to storage. The thiophenetower bottoms are passed into a methyl thiophene tower I9 where methylthiophene is taken as overhead and to storage and methyl thiophene towerbottoms taken to storage to be used in the condensate stripper column I2and/or as a spray in the spray chamber 9.

In a typical operation, the hydrocarbon material charged to thepreheated coil 6 is made up of a rough pentane cut containing varyingamounts of pentenes, obtained from a cracking unit for the conversion ofgas oil into gasoline. Sulfur is charged to the preheater 3, in amountsto produce a mixture at 'I having a weight ratio of sulfur to butanecut, of about 1.0 and the charge rates are adjusted to give a reactiontime of about 0.06 second in the reactor coil 8 at temperatures of 1100F.

The following detailed examples are for the purposes of illustratingmodes of producing alkyl thiophenes in accordance with our invention, itbeing clearly understood that the invention is not to be considered aslimited to the specific manipulations and conditions set forthhereinafter.

Example 1 834 grams of isopentane were charged into a preheater at therate of 40 grams per minute and heated to a temperature of 1080 F. 583grams of sulfur were charged to a separate preheater at a rate of 28grams per minute and heated to a temperature of 1080 F. The two streamswere sent through a mixing nozzle and thence through a baiiied tubereactor of 50 cc. volume constructed of 27% chromium stainless steelmaintained at a temperature of l200 F. The reaction product was quenchedwith a water spray, passed through a small Cottrell precipitator toremove tar mist, and scrubbed through a -hot counter-current caustictower. The liquid product Was cooled, condensed and separated in a watercooler and ice tray. 753 grams of liquid were recovered. Fractionationof the liquid through a 15 theoretical plate column gave 88 grams of aproduct having a boiling range of 107-115" C. Physical measurements and'chemical tests established this fraction to be methyl thiophene.

Example 2 be considered in all respects as illustrative and notrestrictive, reference being had to the ap- Ipendednlaims rather than tothe foregoing description to indicate the scope of the invention.

We claim: l. A process for producing methyl thiophene, which comprisesseparately preheating sulfur and hydhdhrbdn material selectedv iromthegroupV consisting of pantanos, pentenves and pentadienes, having, atleast four carbon atomsuin a straight chains; to temperatures such thatcombining said sultur and saidhyd-rocarbon material will give areactionv mixture havin-g a temperature varying betweenv 850- F'. andabout 1300D F., mixing the preheated sulfur andthe preheated hydrocarbonmaterial, reacting saidpreheated sulfur with said preheated; hydrocarbonmaterial at temperatures varying between 850"l and about 1300"v E. lfora period oitim-eefv not more than about one second to;V yielda methylthiophene-containing mixture, and reducing the temperature of saidmethyl thiophene-containing mixture to less than 850 F.

2,. A process for producing methyl thiophene, which comprises separatelypreheating sulfur and a mixture of pentadienes, pentanes and pentenes,having at least four carbon atoms in a straight chai-n, said pentadienesconstituting less than about 3,0 by volume, of said mixture, totemperatures varying between about ll00 F. and about 12.00 F., mixingthe preheated sulfur and the preheated mixture, reacting said preheatedsulfur with said preheated mixture at tem-peratures varying betweenabout 1100 F, and about l200 F. for a period of timevarying betweenabout 0.01 second and about one second to yield a methylthiophene-containing mixture, and reducing the temperature of saidmethyl thiophene-containing mixture to less than about 850 F.

3. A process for producing methyl thio-phene, which comprises separatelypreheating sulfur and a mixture of pentadienes and pentanes, having atleast four. carbon atoms in a straight chain, said L.

pentadienes constituting less than about 30% by volume of saidmixture'to temperatures varying between about 1100" F. and about 1200F., mixing the preheated sulfur and the preheated mixture,

reacting said preheated sulfur with said preheated mixture attemperatures varying bet'ween about l100 F. and about 1200 F. for alperiod of time varying between about 0.01 second and about one secondto yield a methyl thiophene-containing mixture, and reducing thetemperature of said methyl thiophene-containing mixture to less thanabout 850 F.

fl. A process #for producing methyl thiophene, which comprisesseparately p-reheating sulfur and a mixture of pentadienes and pentenes,having at least four carbon atoms in a straight chain, said pentadienesconstituting less than about 30% -by volume of said mixture, totemperatures varying between about 1100 F. and about 1200 F.,

mixing the preheated sulfur and the` preheated mixture, reacting saidpreheated sulfur with said preheated mixture at temperatures varyingbetween about 1100'u F. and about 1200 F. for a period of time varyingbetween about 0.01 second and about one second to yield a methylthiophenecontaining mixture, and reducing the temperature of methyltl'iiophene-containing mixture to less than about 850 F.

5. A process for producing methyl thiophene, which comprises separatelypreheating sulfur. and a mixture of pentadienes having at least fourcarbon atoms in a straight chain, 4and a diluent which is inert tosulfur and other products of the process, said pentadienes constitutingless than about 30% by volume of said mixture, to temperatures such "Wthat combining said sulfur and said mixture will give a reaction mixturehaving a temperature Varying between 850 E and about 1300 F.. mixins thepreheated sulfur and tho preheated noix.- iuro, reacting said preheatedsulfur. with said prelitt heated-mixture tonlbbraturos. varying`boivyoon. F and about 13002? for-a noriodof uuic of y noi morov than.aboui onoSocond to yield a methyl thionhonorcontaining mixture, andreducing tho.

tonnel-aiutaci Said methyl ihionhonorcontaining loro iban 850 F- forproducing methyl- 'thiophona which compriseslseparately preheatingsulfur and turaot ne bancs, poniendo and pcntadicnos, haiti-nef at leastfou.r carbon aff-omsv in a. straight chain, said pentadienesconstituting less than about 3.0%; byyohinl.ov of said mixture, tovtempera- ,A such.l that combining said sulfur and said mixture. will;sivo. a reaction mixture havinga temperature, varying between 850. F.and about 12005 mixing. thc preheated sulfur and the ,.yineboiwcon 050?F- and about 1300o F. for a period off time. of not morcfthan about onosccond. tov yield a product containing methyl thio-4 nhonornonianoo,ocnicnosA and ncntadionos, roduoing the temperature of said product tolessthan 8506 F., separating pentanes, pentenes and pentadicncs fromsaid. product. and. recycling Said pen.- tanes, pentenes and pentadienesto the process.

7. A process for, producing methyl thiophene, which comprises.separately prohoaiing. sulfur and pantanos having atleast four carbonatomsy in a straight chain, to temperatures Varying between about 11.00F: and about .12000 F., mixing tho preheated sulfur and the preheatedpentanes, reacting said preheated Sulfur with Said prohaatcd pantanos.at temperatures varying between about 11,009 F. and about 1200 F. foraperiod of time, varying between about 0.01 second andv about one secondJofyicld. a methyl thiophonccontaining mixture, and reducing thotempera.- ture of; said methyl thiophene-containing mixture. to. less`than about 8.5.0? E'.

8. A process tor producing methyl thiophone, which comprises separatelypreheating sulfur and p entenes havingV at least fourv carbon'atoms in astraight chain, to temperatures varying between about 110.0? F. andabout 1200" F., mixing the preheated suliur and the preheated pentenes,reacting said preheated sulfur with said preheated pentenes attemperatures varying between about` 11009 and about 1200" F. for aperiod of time varying between about 0 .01 second and about Que. secondto yield a methyl thiophene-containing mixture, and reducing thetemperature of said methyl thiophene-containing mixture to less thanabout. 35.0 E'.

.9. A proceso. for producing methyl thioiohenc, which comprisesSeparately nrohcatine Sulfur. and. a. mixture of. pentanes and penteneshaving at least Ytour carbon atoms in a straight chain, to temperaturesvarying between about 11.00 F- and about 1.2.0.0.` mixing the preheatedSulfur and the preheated mixture, reacting said preheated sulfur withSaid preheated mixture. ai temporatures varying bott/.con about 1100 F.and about 12.0.03 F. for a period of timel varying between about 0.01second and about one second to yield a methyl thiophene-containingmixture, and 11e..- ducing the temperature of said methylthiophenecontaining mixture to less than about 850 F.

l0. A process for producing methyl thiophene, which comprises separatelypreheating sulfur and politonos having at least four carbon atoms in astraight chain, to temperatures such that combining said sulfur` andsaid pentanes will give -a reaction mixture having a temperature varyingbetween 850 F. and about 130,0" F., mixing the preheated sulfur and thepreheated pentanes, reacting said preheated sulfur with said preheatedpentanes at temperatures varying between 850 F. and about 1300" F. for aperiod of time of not more than about one second to yield a productcontaining methyl thiophene, pentanes, pentenes, and pentadienes,reducing the temperature of said product to less than 850 F., separatingsaid pente-nes, pentenes, and pentadienes from said product, andrecycling said pentanes, pentenes, and pentadienes to the process.

.11. A process for producing dimethyl thiophene and ethyl thiophene,which comprises separately preheating sulfur and hydrocarbon materialselected from the group consisting of hexanes, hexenes and hexadienes,having at least four carbon atoms in a straight chain, to temperaturessuch that combining` said sulfur and said hydrocarbon material will givea reaction mixture having a-temperature varying between 850 F. and about1300 F., mixing the preheated sulfur and the preheated hydrocarbonmaterial, reacting said preheated sulfur with said preheated hydrocarbonmaterial at temperatures varying between 850 F. and about 1300 F. for aperiod of time of not more than about one second to yield a dimethylthiopheneand ethyl thiophene-containing mixture, and reducing thetemperature of said dimethyl thiopheneand ethyl thiophenecontainingmixture to less than 850 F.

12. A process for producing dimethyl thiophene and ethyl thiophene,which comprises separately preheating sulfur and a mixture ofhexadienes, hexanes and hexenes, having at least four carbon atoms in astraight chain, said hexadienes constituting less than about 30% byvolume of said mixture, to temperatures varying between about 1100 F.and about 1200 F., mixing the preheated sulfur and the preheatedmixture, reacting said preheated sulfur with said preheated mixture attemperatures varying between about 1100 F. and about 1200 F. for aperiod of time varying between about 0.01 second and about one second toyield adimethyl thiopheneand ethyl thiophenecontaining mixture, andreducing the temperature oi said dimethyl thiopheneand ethylthiophene-containing mixture to less than about 850 F.

13. A process for producing dimethyl thiophene and ethyl thiophene,which comprises separately preheating sulfur and a mixture of hexadienesand hexanes, having at least fo-ur carbon atoms in a straight chain,said hexadienes constituting less than about 30% by volume of saidmixture, to temperatures varying between about 1100 F. and about 1200F., mixing the preheated sulfur and the preheated mixture, reacting saidpreheated sulfur with said preheated mixture at temperatures varyingbetween about 1100 F. and about 1200 F. for a period of time varyingbetween about 0.01 second and about one second to yield a dimethylthiopheneand ethyl thiophenecontaining mixture, and reducing thetemperature of Vsaid dimethyl thiopheneand ethyl thiophene-containingmixture to less than about 850 F.

14. A process for producing dimethyl thiophene 'and ethyl thiophene,which comprises separately preheating sulfur and a mixture of hexadienesand hexenes, having at least four carbon atoms in a straight chain, saidhexadienes constituting less than about 30% by volume of said mixture,-to temperatures varying between labout 1100 F. and about 1200 F.,mixing the preheated sulfur and the preheated mixture, reacting saidpretemperature of said dimethyl thiopheneand ethyl thiophene-containingmixture to less than about 850" F.

15. A process for producing dimethyl thiophene and ethyl thiophene whichcomprises separately preheating sulfur and a mixture of hexadieneshaving at least four carbon atoms in a straight chain, and a diluentwhich is inert to sulfur and to the products of the process, saidhexadienes constituting less than about 30% by volume of said mixture,to temperatures such that combining said sulfur and said mixtures, willgive a reaction mixture having a temperature varying between 850 F. andabout 1300" F., mixing the preheated sulfur and the preheated mixture,reacting said preheated sulfur with said preheated mixture attemperatures Varying between 350" F. and about 1300 F. for a period oftime of not more than about one second to yield a dimethyl thiopheneandethyl thiophene-containing mixture, and reducing the temperature oi saiddimethyl thiopheneand ethyl thiophenecontaining mixture to less than 850F.

16. A process for producing dimethyl thiophene and ethyl thiophene,which comprises separately preheating sulfur and a mixture of hexanes,hex'- enes and hexadienes, having at least four carbon atoms in astra-ight chain, said hexadienes constituting less than about 30% byvolume of said mixture, to temperatures such that combining said sulfurand said mixture will give a reaction mixture having a temperaturevarying between 850 F. and about 1300 F., mixing the preheated sulfurand the preheated mixture, reacting said preheated sulfur with saidpreheated mixture at temperatures varying between 850 F. and about 1300F. for a period of time of not more than about one second to yield aproduct containing dimethyl thiophene, ethyl thiophene, hexanes, hexenesand hexadienes, reducing the temperature of said product to less than850 F., separating hexanes, hexenes, and hexadienes from said product,and recycling said hexanes, hexenes and hexadienes to the process.

17. A process for producing dimethyl thiophene and ethyl thiophene,which comprises separately preheating sulfur and hexanes having at leastfour carbon atoms in a straight chain, to temperatures varying betweenabout 1100 F. and about 12.00 F., mixing the preheated sulfur and thepreheated hexanes, reacting said preheated sulfur with said preheatedhexanes at temperatures varying between about 1100 F. and about 1200CIF. for a period of time varying between about 0.01 second and about onesecond to yield a dimethyl thiopheneand ethyl thiophene-containingmixture, and reducing the temperature of said dimethyl thiopheneandethyl thiophenecontaining mixture to less than about 850 F.

18. A process for producing dimethyl thiophene and ethyl thiophene,which comprises separately preheating sulfur and hexenes having at leastfour carbon atoms in a straight chain, to temperatures varying betweenabout 1100 F. and about 1200 F., mixing the preheated sulfur and thepreheated hexenes, reacting said preheated sulfur with said preheatedhexenes at temperatures varying between about 1100 F. and about 1200 F.for a period of time varying between 13 about 0.01 second and about onesecond to yield a dimethyl thiopheneand ethyl thiophene-containingmixture, and reducing the temperature of said dimethyl thiopheneandethyl thiophenecontaining mixture to less than about 850 F.

19. A process for producing dimethyl thiophene and ethyl thiophene,which comprises separately preheating sulfur and a mixture of hexanesand hexenes, having at least four carbon atoms in a straight chain, totemperatures varying between about 1100 F. and about 1200 F., mixing thepreheated sulfur and the preheated mixture, reacting said preheatedsulfur 'with said preheated mixture at temperatures varying betweenabout 1100 F. and about 1200 F. for a period of time varying betweenabout 0.01 second and about one second to yield a dimethyl thiopheneandethyl thiophene-containing mixture, and reducing the temperature of saiddimethyl thiopheneand ethyl thiophene-containing mixture to less thanabout 850 F.

20. A process for producing dimethyl thiophene and ethyl thiophene,which comprises separately preheating sulfur and hexanes having at leastfour carbon atoms in a straight chain, to temperatures such thatcombining said sulfur and said hexanes will give a reaction mixturehaving a temperature varying between 850 F. and about 1300 F., mixingthe preheated sulfur and the preheated hexanes, reacting said preheatedlsulfur with said preheated hexanes at temperatures varying between 850F. and about 1300 F. for a period of time of not more than about onesecond to yield a product containing dimethyl thiophene, ethylthiophene, hexanes, hexenes and hexadienes, reducing the temperature ofsaid product to less than 850 F., separating said hexanes, hexenes andhexadienes from said product, and recycling said hexanes, hexenes andhexadienes to the process.

` HERBERT E. RASMUSSEN. ROWLAND C. HANSFORD.

REFERENCES CITED The following references are of recordy in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,369,377 Thacker Dec. 13, 19452,410,401 Coffman Oct. 29, 1946 OTHER REFERENCES n Shepard, J. Am. Chem.Soc. 56, 1355-6 (1934).

